William

From Zumipedia

William is a flying Mexican skeleton entity that follows Onezumi after her first death fighting against Negazumi. He appears as a day-of-the-dead doll and gives Onezumi information regarding the Negaverse through clever plot devices like magic post-it notes.

William's place of residence is unknown, but it is supposed he eats lunch South of the brain trees and is believed to socialize with airfish.

His first appearance is in comic #256, which is called "Senor William".

This is bree's favorite character.